Automatically deployable load-line receiving mast structure for limiting deflection of proportionally extendable boom section crane

Abstract

A proportionally extendable multi section boom crane is provided with an automatically erectable mast pivotally carried by one of the boom sections. The mast, which has a secondary sheave on the outer end thereof, normally rests in a stowed position adjacent the boom section on which it is mounted. The load line of the crane extending from the winch at the base of the boom section is trained over the secondary sheave, as well as sheave structure on the outermost end of the outer boom section. Elongated rod structure carried by one of the extendable boom sections outwardly of the crane has coupling means thereon engageable with the mast to initiate erection thereof after the proportionally movable boom sections have been extended a predetermined extent, normally after about 50% extension thereof. Passage of the load line over the mast in an erected position causes bending forces imposed on the extended boom by a weight suspended from the outermost end of the load line produces forces in opposition to the bending moment on the boom sufficient to prevent significant deleterious deflection of the boom from the longitudinal axis thereof.

We claim: 
     
       1. In a crane having a base assembly including a rotatable turret and a base boom section pivotally carried by the turret, a series of proportionally extendable boom sections supported by the base boom section, a winch unit on the base assembly having a winch drum, a primary sheave on the outer end of the outermost of the extendable boom sections, and a flexible load line trained around the winch drum and extending over the sheave on the outermost boom section for lifting of a load by the crane, the improvement comprising: an erectable mast pivotally carried by one of the boom sections, said mast normally being positioned adjacent said one boom section on which it is mounted, said mast being movable to an erect position extending outwardly from said one boom section at an angle with respect to the latter in a direction toward the load line extending between the winch drum and the primary sheave,   there being a secondary sheave on the mast disposed in a position for the load line to pass thereover between the winch drum and the primary sheave; and   means on the boom sections and engageable with the mast for effecting erection of the mast as the boom sections are extended proportionally relative to the base boom section,   said mast and secondary sheave thereon being located such that upon initiation of erection of the mast, the load line extending from the winch drum over the secondary sheave to the primary sheave structure in conjunction with the longitudinal axis of the boom sections defines triangulation geometry,   said load line serving to lift the load and also as a result of said triangulation geometry providing required offsetting boom deflection forces upon initiation of erection of the mast which are a direct function of the overall length and angle of the boom during extension and retraction, and a direct function of the specific load being lifted by the crane boom sections.   
     
     
       2. A crane as set forth in claim 1 wherein said means on the boom section engageable with the mast for effecting erection thereof is operable to erect the mast in response to a predetermined proportional extension of the boom sections relative to the base boom section. 
     
     
       3. A crane as set forth in claim 2 wherein said mast erection means is operable to initiate erection of the mast only after the boom sections have been extended proportionally to a predetermined extent. 
     
     
       4. A crane as set forth in claim 1 wherein said means for effecting erection of the mast includes structure on one of the extendable boom sections engageable with the mast to initiate erection of the mast after the extendable boom section on which the structure is mounted has been extended to a predetermined extent relative to the remaining extendable boom sections. 
     
     
       5. A crane as set forth in claim 4 wherein said mast is mounted on said one boom section at the end thereof remote from said winch. 
     
     
       6. A crane as set forth in claim 5 wherein said structure is mounted on said extendable boom section at the end thereof remote from said winch. 
     
     
       7. A crane as set forth in claim 4 wherein said means for effecting erection of the mast includes connector means pivotally secured to the mast in spaced relationship from the end of the mast pivotally connected to said one boom section, said structure engaging the connector means to initiate erection of the mast after the extendable boom section on which the structure is mounted has been extended to said predetermined extent. 
     
     
       8. A crane as set forth in claim 7 wherein said structure includes elongated rod means pivotally secured to the boom section on which the structure is mounted, extending along the length of the boom sections, and provided with coupling means thereon engageable with said connector means after the extendable boom section on which the structure is mounted has been extended to said predetermined extent. 
     
     
       9. A crane as set forth in claim 8 wherein said connector means includes gimbal means on said mast, said rod means extending through said gimbal means, and said coupling means on the rod means being engageable with the gimbal means after the extendable boom section on which the structure has been extended to said predetermined extent. 
     
     
       10. A crane as set forth in claim 1 wherein said means for effecting erection of the mast is operable to swing the mast through an arcuate path of travel which is non-linear with respect to the proportional extension of the boom sections relative to the base boom section. 
     
     
       11. A crane as set forth in claim 1 wherein said means for effecting erection of the mast is operable to swing the mast through an arc wherein the degree of arcuate travel of the mast is greatest during initial erection of the mast and decreases as the mast approaches and reaches said erect position thereof. 
     
     
       12. A crane as set forth in claim 1 wherein said mast is at an angle of about 80° with respect to the longitudinal axis of the boom sections when the mast is in said erect position thereof. 
     
     
       13. A crane as set forth in claim 1 wherein is provided piston and cylinder means carried by the boom section on which the mast is mounted, and secured to the mast for effecting erection of the mast during proportional extension of the boom sections relative to the base boom section. 
     
     
       14. A crane as set forth in claim 1 wherein is provided means on the mast adjacent said secondary sheave for retaining the load line on the secondary sheave in all angular positions of the mast with respect to said one boom section as the load line unwinds and rewinds on the winch drum. 
     
     
       15. In a crane having a base assembly including a rotatable turret and a base boom section pivotally carried by the turret, a series of proportionally extendable boom sections supported by the base boom section, a winch unit on the base assembly having a winch drum, a primary sheave on the outer end of the outermost of the extendable boom sections, and a flexible load line trained around the winch drum and extending over the sheave on the outermost boom section for lifting of a load by the crane, the improvement comprising: an erectable mast pivotally carried by one of the boom sections, said mast normally being positioned adjacent said one boom section on which it is mounted, said mast being movable to an erect position extending outwardly from said one boom section at an angle with respect to the latter in a direction toward the load line extending between the winch drum and the primary sheave,   there being a secondary sheave on the mast disposed in a position for the load line to pass thereover between the winch drum and the primary sheave; and   means on the boom sections and engageable with the mast for effecting erection of the mast after the boom sections have been partially extended to a predetermined extent and as the boom sections are further extended proportionally relative to the base boom section to an extent that a load to be picked up by the load line would otherwise impart an undesirable side deflection force on the extended boom,   said mast and secondary sheave thereon being located such that upon initiation of erection of the mast, the load line extending from the winch drum over the secondary sheave to the primary sheave structure in conjunction with the longitudinal axis of the boom sections defines triangulation geometry,   said load line serving to lift the load and also as a result of said triangulation geometry upon initiation of erection of the mast providing required offsetting boom deflection forces as a direct function of the overall length and angle of the boom during extension and retraction, and a direct function of the specific load being lifted by the crane boom sections.   
     
     
       16. A crane as set forth in claim 15 wherein the mast is located along the boom sections in disposition such that when the mast is in the erect position thereof, the length of the load line extending from the winch drum to the secondary sheave is at a greater angle with respect to the longitudinal axis of the boom sections than the angle of the length of the load line extending from the secondary sheave to the primary sheave with respect to the longitudinal axis of the boom sections. 
     
     
       17. A crane as set forth in claim 15 wherein the mast is located along the boom sections in disposition such that when the mast is in the erect position thereof, the length of the load line extending from the winch drum to the secondary sheave is approximately at the same angle with respect to the longitudinal axis of the boom sections as the angle of the length of the load line extending from the secondary sheave to the primary sheave with respect to the longitudinal axis of the boom sections. 
     
     
       18. A crane as set forth in claim 15 wherein said mast is mounted on the outermost end of the base boom section remote from the winch unit, said mast erection means being mounted on the extendable boom section in closest proximity to the base boom section when the boom sections are fully extended. 
     
     
       19. A crane as set forth in claim 15 wherein said mast is mounted on the extendable boom section in closest proximity to the base boom section when the boom sections are fully extended, and said mast erection means is mounted on the extendable boom section in next closest proximity to the base booms section when the boom sections are fully extended. 
     
     
       20. In a crane having a base assembly including a rotatable turret and a base boom section pivotally carried by the turret, a series of proportionally extendable boom sections supported by the base boom section, a winch unit on the base assembly having a winch drum, a primary sheave on the outer end of the outermost of the extendable boom sections, and a flexible load line trained around the winch drum and extending over the sheave on the outermost boom section for lifting of a load by the crane, the improvement comprising: an erectable mast pivotally carried by one of the boom sections, said mast normally being positioned adjacent said one boom section on which it is mounted, said mast being movable to an erect position extending outwardly from said one boom section at an angle with respect to the latter in a direction toward the load line extending between the winch drum and the primary sheave,   there being a secondary sheave on the mast disposed in a position for the load line to pass thereover between the winch drum and the primary sheave; and   means on the boom sections and engageable with the mast for effecting erection of the mast after the boom sections have been partially extended to a predetermined extent and as the boom sections are further extended proportionally relative to the base boom section to an extent that the extendable boom sections no longer overlap the base boom section and one another relatively to an extent that undesirable side deflection of the boom sections would otherwise occur when a load is picked up by the load line,   said mast and secondary sheave thereon being located such that upon initiation of erection of the mast, the load line extending from the winch drum over the secondary sheave to the primary sheave structure in conjunction with the longitudinal axis of the boom sections defines triangulation geometry,   said load line serving to lift the load and also as a result of said triangulation geometry upon initiation of erection of the mast providing required offsetting boom deflection forces as a direct function of the overall length and angle of the boom during extension and retraction, and a direct function of the specific load being lifted by the crane boom sections.   
     
     
       21. A crane as set forth in claim 20 wherein said mast erection means is operable to initiate erection of the mast when the degree of overlap of the boom sections becomes less than about 50%.